1. Field of the Invention
The present invention relates to a wheelset steering apparatus and a wheelset steering method for the truck of railway vehicles.
2. Description of the Prior Art
According to, for example, A. H. Wickens, "Steering and Dynamic Stability of Railway Vehicles", Vehicle System Dynamics, 1975/76, P15-46, the self-steering property of a wheelset is defined as an effort of movement of running of a wheelset 2, 2', with reference to a truck illustrated in FIG. 11, which is elastically supported on a truck frame 1, toward to a radial direction on a curved track. This self-steering property of the wheelset on the curved track is known to be better if the bending stiffness, k.sub.b, of the wheelset 2, 2' (hereinafter called as `bending stiffness`) as given by Equation (1) is smaller, and the shearing stiffness, k.sub.s, between the wheelsets 2, 2' (hereinafter called as `shearing stiffness`) as given by Equation (2) is larger. EQU k.sub.b =k.sub.x .multidot.b.sup.2 ( 1)
where
k.sub.x is a longitudinal spring constant per wheel; and PA0 b is a half of the lateral distance of the wheelset 2, 2'. ##EQU1## where k.sub.y is a lateral spring constant per wheel; PA0 a is a half of the longitudinal distance between the wheelsets 2, 2'; and PA0 k.sub.rs is a shearing spring constant directly provided between the wheelsets 2, 2'.
Meanwhile, the running stability on a straight track (the property of being runnable stably with a hunting motion of the wheelset being not sent forth but turning to damped vibration) is known to be better if the bending stiffness k.sub.b is larger and the shearing stiffness k.sub.s is smaller. Such relation, however, calls for inconsistent characteristics of the truck. Hence, there is a difficulty that either one of the two should have more importance attached and either one of the two must be sacrificed unavoidably.